This invention relates to funnels in general, and specifically to funnels that are used with cloth and/or paper inserts to filter the liquid poured inside the funnel.
The convenience and advantages of using paper and cloth filters with funnels has been widely recognized. In combination with funnels, these type of filter inserts provide an inexpensive and relatively maintenance free filter unit. The filter inserts are periodically replaced with fresh new filters, and the old filters are frequently discarded, or in some cases, washed or cleaned and reused. As a funnel typically lasts for many years and filter inserts are in ample supply, this type of filter assembly has become a desirable commodity, and consequently have become commercially popular. While their use is especially well known in the coffee industry, this filter assembly is useful in other fields as well, such as in the filtering of cooking oil for reuse.
The combination of cloth or paper filter inserts and funnels, however, does not come without a major drawback: the inserts tend to stick to the sides of the funnel. This has several undesirable effects. For instance, the portions of the filter insert that adhere to the sides of the funnel are incapable of filtering any liquid through the sides of the filter insert. Therefore, any filtering that occurs as the liquid passes through the filter insert is at the bottom of the insert where the fluid may flow unobstructedly through the filter insert and out the funnel exit orifice. Thus, most of the filtering capacity of the funnel is compromised when the sides of the filter inserts stick to the funnel. As a result, the rate of liquid flow through the filter insert is relatively slow, and the amount of time needed to filter a liquid is relatively large. The adherence of the inserts to the walls of the funnel also makes it difficult to remove the insert for cleaning or to replace it with another one.
Various types of funnel construction have been proposed in the art to overcome this problem. For example, U.S. Pat. No. 4,765,896 teaches the use of stepped concentric sidewalls and wire baskets with funnels to keep a filter insert from adhering to the sides of the funnel. While some success has been achieved by the use of stepped concentric sidewalls and wire baskets in preventing adherence of a filter insert to the sidewalls of a funnel, this construction accomplishes little toward increasing the rate of liquid flow through the filter insert and out of the funnel. That is because the stepped concentric sidewalls tend to trap the fluid after it flows through the filter.
This trapping of the fluid between the steps of the sidewalls or wire baskets and a filter insert has several consequences. First, some of the filtered fluid flows back through the filter and eventually is filtered again as it passes through the bottom of the filter. This double filtering of the fluid is an unnecessary waste of the capacity of the filter as well as an unnecessary increase in valuable time. Second, some of the liquid that is trapped between the filter insert and the sidewalls of the funnels of the prior art remains trapped until the filter insert is removed. Consequently, the filter insert is often dripping wet when it is removed and replaced, and the trapped fluid often splashes down into and through the funnel. Aside from creating a mess, this effectively wastes a portion of the filtered fluid. Third, depending on the frequency of use of the funnel, the liquid being filtered, and how long the liquid is trapped, sediment from the trapped liquid may buildup in the funnel over time. This build up is likely to be unclean, unsightly, and difficult to remove.
The funnels of the prior art are therefore disadvantageous when used with filter inserts because they lead to inefficient double filtering of the fluid poured into the filter insert, increase the amount of time necessary to filter a liquid through the funnel, waste some portion of filtered fluid over the course of time, and render a funnel unsightly and difficult to clean and maintain during extended use of the funnel.